espresso: Fixed MMS settings

Set the maxMessageSize to 300kb as that is what most carriers set
as the maximum sending size.

Adjusted the max width/height values a bit to something that goes
better with the 300kb file size limit.

Change-Id: Id921b9e26bc62e8c01786161d9b252ecfb9df335

overlay/packages/apps/Mms/res/xml/mms_config.xml

@@ -22,13 +22,13 @@
 
 <mms_config version="3">
     <!-- Maximum message size in bytes for a MMS message -->
-    <int name="maxMessageSize">614400</int>
+    <int name="maxMessageSize">307200</int>
 
     <!-- Maximum height for an attached image -->
-    <int name="maxImageHeight">1944</int>
+    <int name="maxImageHeight">768</int>
 
     <!-- Maximum width for an attached image -->
-    <int name="maxImageWidth">2592</int>
+    <int name="maxImageWidth">1024</int>
 
     <!-- User-Agent parameter used in MMS http request -->
     <string name="userAgent">Android-Mms/0.1</string>